A number of oxides and oxyhalides of sulfur, selenium and phosphorus can be utilized as liquid phase cathode reactants in primary lithium battery cells. Such oxides and oxyhalides include sulfur dioxide, phosphorous oxychloride, selenium oxychloride, thionyl chloride and sulfuryl chloride. These compounds can be dissolved in an inert or organic solvent, mixed with each other or used as the sole electrolyte solvent.
One of the most promising of these primary cell systems is the lithium-thionyl chloride cell. One of the most successful cell formulations as disclosed and claimed in U.S. Pat. No. 364,575 uses a solution of lithium aluminum chloride in thionyl chloride as the electrolyte and a Teflon-bonded carbon electrode as the cathode.
It is also disclosed in U.S. Pat. No. 364,575 that the use of sulfuryl chloride as the electrolyte solvent affords the highest open circuit voltage of any known primary cell. The difficulty with the use of sulfuryl chloride is that its closed circuit voltage, capacity, and as a result its energy density is inferior to that of thionyl chloride which has been the most popular of the oxychloride solvents for primary cells.